Merge pull request #906 from rogday:yolov4x-mish

Author: alalek

testdata/dnn/download_models.py

@@ -874,6 +874,11 @@ def get_confirm_token(response):  # in case of large files
         url='https://github.com/AlexeyAB/darknet/releases/download/darknet_yolo_v4_pre/yolov4-tiny.weights',
         sha='d110379b7b86899226b591ad4affc7115f707157',
         filename='yolov4-tiny.weights'),
+    Model(
+        name='YOLOv4x-mish',  # https://github.com/opencv/opencv/issues/18975
+        url='https://github.com/AlexeyAB/darknet/releases/download/darknet_yolo_v4_pre/yolov4x-mish.weights',
+        sha='a6f2879af2241de2e9730d317a55db6afd0af00b',
+        filename='yolov4x-mish.weights'),
     Model(
         name='GSOC2016-GOTURN',  # https://github.com/opencv/opencv_contrib/issues/941
         downloader=GDrive('1j4UTqVE4EGaUFiK7a5I_CYX7twO9c5br'),